For many years the practice in correcting errors made by a typist was to either use a gum eraser to abrade away the ink on the paper or to paint over the error with a paint colored to match the color of the paper. More recently there have been developed two types of erase tapes which are struck with the letter in error and "erase" it. One is a cover-up tape in which a second ink, color to match the color of the paper, is printed over the contrasting color typing ink (which will be known hereafter as an overprint erase tape); a second type is a tape in which the ink is actually lifted off the paper and carried off by the erase tape. With this type (which will be known hereafter as a liftoff type of erase tape) special liftoff inks must be used.
Both the liftoff and the overprint type of erase tapes, however, have certain things in common. One is that each is only useful a single time per unit spacing, that is, the tape can only be used to erase one letter and then a new section of tape must be supplied to correct the next error. For this reason, the tapes are usually supplied on single reels which are threaded past the typing head and interposed between the characters striking the inked ribbon and the paper. They are wound a single space ahead at a time, and are discarded when they have been wound all the way from one end to the other.
Clearly, under these circumstances, it is essential that the gradually unwinding spool of tape be kept under tension so that the tape does not belly or sag into the remainder of the typing machinery. For this reason it is essential to apply a continuous tensioning force to the tape. The tensioning devices available in the prior art have not adequately performed their function. Therefore, until the present invention, it had been a need of the art to provide an improved tensioning device.